Alcohol processes such as Ethanol and
Methanol processes are prime candidates
for DCS based advanced controls. From
extensive studies, we have been able to
identify the true relationships between
the variables and we provide powerful
and robust advanced controls solutions.

The alcohol industry has so far not
benefited to the fullest extent from
advanced control solutions. This is
typical of small units or processes
where MPC (model-predictive control) or
Neural Network technologies are rather
costly to implement. This situation fits
in well with our proprietary DCS-based
advanced control schemes which are
geared towards processes that lack
significant multivariable interactions.
Of course when the need calls for true
MPC technology, we offer MPC also, as
needed.

We are presently developing packaged solutions for alcohol plants as we have done
for Polyethylene and polypropylene plants.

Application of PiControl technology to
Ethanol plants will improve plant-wide
key performance indicators and accrue
the following benefits:

Increase ethanol production rate by
automatically identifying and pushing
against the active constraint,
continuously in real-time. Constraints
include process, equipment, economic or
market constraints at any given time.
The overall approach constantly moves
the process in the most profitable
direction.

Minimize fermentation batch cycle
time using Expert System based adaptive
sequence technology. This increases the
overall ethanol throughput because of
increase in fermenter capacity.

Maximize fermentation yields to
ethanol by optimizing fermentation
process conditions using both the Expert
System and an online real-time
optimizer.

Minimize alcohol losses in the three
distillation column product streams by
improved control of distillation
variables and product specifications
using various advanced process control
schemes. The control schemes minimize
alcohol losses from stillage, fusel oil
and water.

Minimize water addition to ferment
beer mash with higher levels of solids.
This reduces the cost of handling and
treating the water later. In addition,
higher solids result in higher "beer"
yields in the same or less time.

Improve plant-wide process control
quality by reducing deviation of product
specifications and other critical
controlled variables from their setpoints. PiControl technology performs
closed-loop dynamics identification
followed by controller parameter
optimization to provide optimal control
of all variables. PiControl engineers
will custom-analyze every single
existing controller in the plant and
look for control improvements through
re-configuration, new algorithms or
optimized tuning.

For the Ethanol Process, we provide PID
tuning, advanced control and
optimization for the following areas:

HOT SLURRY

The milled grain is mixed with
process water, the pH is adjusted to
about 5.8, and an alpha-amylase enzyme
is added. The slurry is heated to 180–190°F
for 30–45 minutes to reduce viscosity.

PRIMARY LIQUEFACTIONThe slurry is then pumped
through a pressurized jet cooker at
221°F and held for 5 minutes. The
mixture is then cooled by an atmospheric
or vacuum flash condenser.

SECONDARY LIQUEFACTION

After the flash condensation cooling,
the mixture is held for 1–2 hours at
180–190°F to give the alpha-amylase
enzyme time to break down the starch
into short chain dextrins. After pH and
temperature adjustment, a second enzyme,
glucoamylase, is added as the mixture is
pumped into the fermentation tanks.

SIMULTANEOUS SACCHARIFICATION
FERMENTATION

Once inside the fermentation tanks, the
mixture is referred to as mash. The
glucoamylase enzyme breaks down the
dextrins to form simple sugars. Yeast is
added to convert the sugar to ethanol
and carbon dioxide. The mash is then
allowed to ferment for 50–60 hours,
resulting in a mixture that contains
about 15% ethanol as well as the solids
from the grain and added yeast.

DISTILLATION

The fermented mash is pumped into a
multi-column distillation system where
additional heat is added. The columns
utilize the differences in the boiling
points of ethanol and water to boil off
and separate the ethanol. By the time
the product stream is ready to leave the
distillation columns, it contains about
95% ethanol by volume (190-proof). The
residue from this process, called
stillage, contains non-fermentable
solids and water and is pumped out from
the bottom of the columns into the
centrifuges.

DEHYDRATION

The 190-proof ethanol still contains
about 5% water. It’s passed through a
molecular sieve to physically separate
the remaining water from the ethanol
based on the different sizes of the
molecules. This step produces 200-proof
anhydrous (waterless) ethanol.

CO-PRODUCT PROCESSING

During the ethanol production process,
two valuable co-products are created:
carbon dioxide and distillers grains.

As yeast ferment the sugar, they release
large amounts of carbon dioxide gas. It
can be released into the atmosphere, but
it is commonly captured and purified
with a scrubber so it can be marketed to
the food processing industry for use in
carbonated beverages and flash-freezing
applications.

The stillage from the bottom of the
distillation tanks contains solids from
the grain and added yeast as well as
liquid from the water added during the
process. It is sent to centrifuges for
separation into thin stillage (a liquid
with 5–10% solids) and wet distillers
grain. Some of the thin stillage is
routed back to the cook/slurry tanks as
makeup water, reducing the amount of
fresh water required by the cook
process. The rest is sent through a
multiple-effect evaporation system where
it is concentrated into syrup containing
25–50% solids. This syrup, which is high
in protein and fat content, is then
mixed back in with the wet distillers
grain (WDG).